The reproduction of documents as images on media sheets generally requires the generation of a source file, the translation of the source file, and the interpretation of the translated file to reproduce an image of the source data. In the first stage, a user can generate or edit a source document data file utilizing an application program or imaging device. The source data file may include text, images, and graphics as well as font characteristics, format codes, and the like.
To print the source file onto a substrate, the source data file is translated to a page description format that is implemented with a page description language (PDL), such as PostScript, PDF, PCL, TIFF, SVG, Metro, or the like. The device-dependent data may be translated to a device-independent color space, such as CIELAB, XYZ, a spot color space such as Pantone, or a profile connection space (PCS). PCS space is defined by one of the profiles that have been developed by the International Color Consortium (ICC). The PDL commands and device-independent color data are provided to a marking or print engine for processing. The print engine decomposes the device-independent data and converts the device-independent color data to the color space of an output device, such as an image output terminal (IOT). The decomposition of the document file includes the interpretation of the PDL commands, which enables the print engine to optimize the imaging of individual objects on a page. The printing device may then be used to generate the raster data that are used to print color images of the document.
Generation of the device-independent data also includes the specification of output parameters for the printing of a job at the printing device. Output parameters that may be selected or adjusted for output of a job include the color, weight, coating, opacity, and white point of the substrate on which a document is reproduced.
Another output parameter that may be defined for a print job is referred to as a rendering intent or render intent. Examples of rendering intents include “perceptual,” “saturation,” “absolute calorimetric,” and “relative colorimetric,” all of which are specified by the ICC. Another rendering intent example is “pure.” This rendering intent is specified by the Color Encoding Standard, which is part of the Xerox System Integration Standard published by Xerox Corporation, Palo Alto, Calif., July 1991, XNSS 289107 (hereinafter “The Xerox Color Encoding Standard”). The Xerox Color Encoding Standard describes three reference color systems that attempt to provide device independent color between devices, such as workstations and printers. Each rendering intent can specify an enhancement for a particular context. For example, “perceptual” makes photographic images more life-like, while “saturation” makes colors brighter and is useful to enhance the look of pie charts, for example. Some output parameters, such as rendering intents, may be specified for different portions or objects of the same page. For example, different rendering intents may be specified for a photographic image, a pie chart, and text that are presented on the same page.
Rendering intents can assist a printing device in producing a higher quality output. One set of intents may specify a particular halftone that is appropriate for a particular object. For example, a high frequency halftone may be especially appropriate for the edges of text and line art, while a lower frequency halftone may be specified for areas in which the range of color intensities are more important. “Glossmarks,” for example, may be implemented utilizing rendering intents that specify complementary halftones. Also, compression may be used within a real time format that drives a print engine. A rendering intent may be used to identify an appropriate compression for an object, such as lossy compression for JPEG images, for example, or lossless compression, such as flate, LZW, CCITT Group 4 methods for line art, and text.
A user, such as a graphic designer, may design a document with an image or graphic as background along with any image object to render white texts scattered across the complete page or a portion of the page in order to create a perception of white text on the designed background. Such an approach is a challenge to RIP the background and white text in particular.
The RIP system is really concerned about the quality and in general (not considering the scenario) different kinds of objects are assigned to different rendering intents and compressed differently. An incorrect tag assignment can create a ghosting effect, which can negatively impact the final image quality for small image white text in a rendered image. Considering an image as a background and small image white texts on images, the imager may assign the perceptual rendering intent as tag values for all the pixels in the image. In this scenario, from a perceptual quality perspective the entire image along with the tiny text produces a quality defect due to the background image pixels bleeds into white text region when printing.